The present invention relates to intraocular lenses (IOLs) formed of a material such as silicone or a hydrogel that allows the lens to be folded, rolled or otherwise deformed or compressed and, more particularly, an improved apparatus and method for deforming or compressing IOLs of that type and positioning them for insertion into the eye of a patient.
IOLs were developed a number of years ago to replace a clouded natural lens, called a cataract. Cataracts cause individuals to lose their sight, either partially or completely, because clouding prevents light and an image from being transmitted through the lens onto the retina. When the clouding becomes severe, an individual can no longer see. Replacement of the natural lens with an IOL has become an accepted procedure for alleviating the symptoms of a cataract.
Various surgical procedures have been developed for removing a cataract, ranging from physically lifting the lens from the membrane that encapsulates the lens to emulsifying the lens through the use of sound waves and suction equipment. It has been found that this latter procedure, known as phacoemulsification, is advantageous because a much smaller incision is required in the eye, 3 mm or smaller, than other techniques where the lens is removed in tact. A smaller incision is desirable because if sutures are used to close it, the eyeball is deformed less than for larger incisions which are typically up to 6.5-8 mm. Further, with incisions under 3 mm, sutures are generally not required and the incision heals itself. The lack of sutures offers an even further assurance that the ocular globe or eyeball will not be deformed.
A number of different attempts have been made to develop IOLs which can be inserted through the smaller incision openings. Before the availability of IOLs formed of a soft material that could be deformed or compressed, various techniques were attempted to develop a small profile IOL, ranging from forming lenses with a narrower lateral dimension to various types of lenses that could be dismantled or manipulated and rebuilt in the eye.
After IOLs formed of silicon or a hydrogel material became available, IOLs could be folded, rolled or otherwise deformed or compressed so that they could be inserted into the eye through a much smaller incision than previously possible. Such lenses are described and shown, for example, in U.S. Pat. No. 4,573,998 to Mazzocco.
Various techniques and equipment have been developed for folding soft IOLs and inserting them into the eye. These include the use of forceps with relatively long blades which can engage an IOL and hold it in a folded position while it is inserted into the eye as shown, for example, in U.S. Pat. Nos. 5,007,913; 5,100,410 and 5,178,622. The disadvantage of these forceps devices is that they are difficult to operate. As the forcep blades release the IOL, its positioning is not tightly controlled within the eye and movement of the forcep blades could cause the incision to be enlarged. In addition, any movement close to the inner surface of the cornea is undesirable because the forcep blades or lens could rub against the endothelial cells on the inner surface of the cornea, which are not regenerative, and cause permanent damage. Since the forceps are manually squeezed by the surgeon, there is also the possibility that too much pressure could damage various portions of the IOL.
Another type of insertion instrument which has been developed includes a chamber in which an IOL is inserted. The IOL is folded, rolled or otherwise deformed or compressed during the insertion process. The IOL is then pushed or expressed out of an elongated tip by a plunger after the tip is inserted into the eye.
While this type of inserter has the advantage of an elongated tip, which does not have to be opened or closed, projecting through a small incision for precise placement of an IOL, known designs have various moveable parts that are complicated to fabricate and assemble or the folding process requires several steps which prolong and complicate the surgical procedure.
For example, a number of inserters have been developed where an envelope or paddle is moved to project from the distal tip of the inserter, which operates to fold the IOL as it is pulled back into the inserter. The IOL is implanted when the paddle is afterward moved to project from the tip by a physician. See, for example, U.S. Pat. Nos. 4,836,201; 4,880,000; 4,934,363 and 5,098,439. Others have jaw-like portions that operate to fold the IOL as they close or telescopic sections that move relative to each other to hold the lens after it has been folded. See, for example, U.S. Pat. Nos. 4,714,373; 4,747,404 and 4,834,094.
An inserter was also developed, as shown in U.S. Pat. No. 4,919,130, where a cannula is designed to receive an IOL that is partially folded. A first plunger pushes the IOL through a rigid chamber of gradually diminishing diameter to fold it completely. A second plunger then pushes the IOL out of the cannula and into the eye.
In another inserter, shown in U.S. Pat. No. 4,681,102, an IOL is placed in an open cartridge which has two tabs or wing-like sections that are hinged together. The IOL is folded as the sections are closed. The cartridge is then placed in an inserter where an insertion cone, with an opening coextensive with the opening in the cartridge, is either placed over or formed adjacent to the cartridge. A single plunger is used to push the folded lens through the insertion cone and into the eye.
Because of the moving parts in many of the folding devices discussed above, the IOL can easily be pinched or torn during the folding or insertion process. In addition, folding and loading require a certain amount of manual manipulation of the IOL, which takes time and complicates the procedure. In the device where a cannula is used, a first plunger is used to fold the lens, which must be removed and replaced by a second plunger for inserting the lens in the eye.
Thus, there is a perceived need for an apparatus and method for folding an IOL and positioning it for insertion in the eye, which are less complicated than known devices and methods and eliminate moving parts which can pinch and tear the IOL and unneeded steps in the folding process.